16 NILS ODHNER, NORTHERN AND ARCTIC INVERTBBRATES. III. OPISTHOBRANCHIA ETC. 



b. Spire prominent; shell elongated; outer lip a little compressed above. 

 Head-lobe deeply incised behind. L. 17 mm, animal; 7 mm, shell; 

 uncini denticulated 



Ph. Urna (Brown 1827) = lineolata (Couthouy 1839). 

 Uncini smooth ; sculpture consisting of distinct points without 

 connecting lines var. frigida Knipowitsch 1896. 



B. narrow, scarcely curved, 



1. on each side 6 (radula 6.1.0.1.6); shell striated. 



a. Shell latticed on the surface; outer lip scarcely compressed. Animal with 

 the mantle incised behind; colour white, with opaque white spöts. L. 17 

 mm, animal; 6 mm, shell Ph. pruinosa (Clark 1828). 



Pl. III % ?,. 

 h. Hliell witii spiral sculiiture oiily; outer lip liiglily compressed beliind. L. 10 mm. 



Ph. flexuosa M. Saes 1870. 



2. on eacli siile 2 (radnia 2.1.0.1 .2); shell smooth, verv broad (like a Diaphana). Mantle incised 

 behind. L. 2,5 mm. shell Ph. velntinoides G. O. Sahs 1878 ='? ventrieosa (.Ieffbeys 18fi7). 



Fam. Aplysiidae. 



1. Parapodial lobes separated in front (subfani. Aplysiinse). Rhinophores placed be- 

 fore the ends of the dorsal lobes; mantle open at the back; body smooth; ra- 

 dula oc . 1 . 00 Aplysia Linné. 



Parapodial lobes separated only by the genital groove (subfam. Dolabriferinae). Rhinophores as in Aplysia: 

 mantle elosed. withnnt dorsal opening: body mostly rough or warty: radula x. l.a Dolabrifera ftKAY. 



o 



Aplysia Linné i 766. 

 Tethya Linné 1758.' 



Rhinophores and tentacles cylindrical with a longitudinal furrow in front. Co- 

 lour dark-reddish, brownish or greenish with white döts. Shell an o väte, concave 

 plate of a påle yellowish colour. L. 70 — 150 mm, animal; 17 mm, shell 



A. rosea Rathkr 1799 = punctata Cuvier 1803. 



Pl. II figs. 4—7. 



Dolabrifera Gray 1847. 



Body elevated; tentacles and rhinophores very low and widely expanded. Colour dark olive-brownish, 

 the body-sides and the sole darkest, the sides of tlie back with reddish brOAvn spöts. Shell elongated. truneated 

 in front, with a prominent spire; its eolonr påle yellowish. L. 25 mm. animal: 10. ö mm, shell 



D. Hollbölli Bergh 1872. 



Fam. Pleurobranchidae. 



l*Jeurol»raii('lnis Cuvier 1804. 



Radula oo.2.go. Tentacles replaced by a velum. 



Gill-plume pectinated with about 20 teeth on each side; rhinophores cylindrical, 



' The name Tethys was api>lied by Linné in 17fi(i to a Nndihranch. 



